Rates of interdiffusion of the Pt-group metals Ir, Pd, Pt, Rh and Ru with nominally pure Ni were characterized. Interdiffusion coefficients were estimated by analyzing the measured diffusion profiles. In the composition range studied (no greater than 10wt% of the Pt-group metal), the interdiffusion coefficients displayed little concentration dependence, but the values could differ by an order of magnitude. In order to rationalize the dependence of the interdiffusion coefficient on atomic number, the data were compared with values for other elements which were already in the literature. A systematic trend was observed: elements furthest from the center of the period displayed the largest values and elements at the center the smallest. It appears therefore that the magnitude of the interdiffusion coefficient correlates strongly with the atomic radius of the interdiffusing transition metal species. The results suggested the existence of a binding energy between the vacancies and the impurity species. It was believed that the interdiffusion data were of considerable use to those designing new and novel grades of superalloy for high temperature applications.

Interdiffusion of the Platinum-Group Metals in Nickel at Elevated Temperatures. M.S.A.Karunaratne, R.C.Reed: Acta Materialia, 2003, 51[10], 2905-19